Why does M. abscessus need different antibiotics than MAC?

Question

Hello doctor,

I hope you are well.

I am 29 years old and was recently diagnosed, after several months of testing, with a mycobacterial lung infection. After several months of tests, I learned that I have a mycobacterial lung infection. My pulmonologist is currently trying to determine whether it is MAC or Mycobacterium abscessus, and I understand that this difference is important for treatment.

Could you help me understand why Mycobacterium abscessus needs a different antibiotic treatment than MAC, especially for someone my age? I have been waiting almost six weeks for the culture results, and during this time, my symptoms, especially cough and fatigue, have continued to get worse.

I am confused about why it takes so long to confirm the precise strain and whether there are hazards or factors to consider before starting therapy while waiting for the final culture results. I am concerned that the delay in diagnosis may cause me to miss necessary treatment.

I would really appreciate any clarification on these questions and any advice on what I should do next.

Thank you for your time and support.

Answer 1

Hello,

Welcome to icliniq.com.

Thank you for getting in touch and letting me know about your concerns. I know it is stressful and frustrating to deal with ongoing symptoms and not have a clear diagnosis yet.

Your healthcare team is working to distinguish Mycobacterium avium complex (MAC) from Mycobacterium abscessus. These infections are quite different, and each needs its own treatment plan. MAC usually grows slowly and is managed with several months of oral antibiotics. In contrast, Mycobacterium abscessus is resistant to standard therapies and often requires intensive intravenous treatment. Even with appropriate therapy, the response may be less predictable.

If treatment starts before the exact infection is identified, it might not work and could make the infection worse. That is why it is important to confirm which organism is causing the problem.

The delay you are experiencing is mostly because these bacteria grow slowly in laboratory cultures. Once they start to grow, more tests are needed to find out exactly which type they are and which antibiotics will work best. Although this takes time, it is important to choose the right treatment.

For stable patients, doctors usually wait for confirmed results before starting treatment, since using the wrong antibiotics can make future treatment less effective. But if symptoms are getting worse or the disease seems to be progressing, your pulmonologist might start a temporary treatment and then adjust it once the results are in.

Since your cough and fatigue are getting worse, I recommend letting your pulmonologist know about these changes. They can review your condition and decide if your treatment plan needs to be updated.

I hope this helps clear things up.

Please reach out if you have any more questions or concerns.

Thank you.